It’s official, all the social networking sites have started adding “promoted” tweets/posts/places to your news feed. It’s no surprise considering that Twitter, with its “promoted tweets,” recently said it has a “truckload of money in the bank”.

Today Foursquare is launching its version of search ads, Promoted Updates.

Promoted Updates operate like Google’s promoted listings or Twitter’s promoted tweets. They are pay-per-action ad placements that only appear when a user is searching for a venue in Foursquare’s Explore tab.

Foursquare determines a user’s current location and check-in history before displaying a Promoted Update. The ads are powered by the same recommendation engine as its Explore feature. All of the paid placements will be clearly labeled at the top of the feed; they can include a store’s recent news, photos or specials.

Foursquare has partnered with about 20 merchants, from small mom and pop shops to national chains like Best Buy, to launch the pilot program. In the next few months, Foursquare hopes to turn Promoted Updates into a self-service tool merchants of all sizes can use on its platform.

As snapshots through time, Olympic posters provide a fascinating record of our world, a lens through which we can explore links between sports and art, politics and place, commerce and culture. A Century of Olympic Posters offers an intensely visual representation of the modern Games, and shows the evolution of the Olympic Games poster as well, from the first official poster for Stockholm in 1912 right up to the present.

As of February 2012, 5 million guest nights have been booked worldwide since the site’s launch in 2007, with a 500% growth in the past year and accommodations in over 19,000 cities.

Airbnb Global Growth Infographic

I’ve now stayed at two properties (one in San Diego and one in Santa Barbara) and I’m officially on the Airbnb bandwagon. Here’s why:

1. Comfort: After traveling so much in my career, I’ve grown weary of the generic, cookie cutter look and feel of hotel rooms, even 5-star accommodations. Staying at an AirBnb is like staying at a friend’s house, with all the comforts and spaciousness of a home, like a kitchen and a comfy living room with books and magazines to peruse.

2. Amenities: I’ve started to deplore how hotels nickel and dime guests, especially when it comes to wifi and water. Both Airbnbs I’ve stayed at offered free, secure wifi and purified drinking water. It might sound trivial, but I feel like water and wifi should be included in a guest’s stay. And at our Santa Barbara rental, the owner provided two bikes, with bike locks and helmets for guests. I can’t tell you how awesome it was to arrive and jump right onto the bike to explore the city. Plus, there was free street parking just feet away from the entrances at both properties.

3. Cost: Bottom line, you get a lot more for a lot less at an Airbnb. And you don’t have to pay for all the hidden costs of hotels.

Not all people will love Airbnb (especially those enamored by turn-down and room service). But I get a feeling a growing number of folks will like what Airbnb has to offer (on both the demand and supply side) and it’s going to take a big bite out of the hotel industry pie.